Apparatus for controlling the dose of irradiation

ABSTRACT

An apparatus for controlling dose of irradiation comprising a first barrier body (1) arranged between a conveyer (5) and an irradiation device (6) located opposite to said conveyer (5), the first barrier body (1) being slidably movable along a running direction of the conveyer (5), and a second barrier body (2) arranged in juxtaposition with the first barrier body (1) and slidably movable along the running direction of the conveyer (5), a distance between the first barrier body (1) and the second barrier body (2) being so adjustable as to control the dose of irradiation to the product.

BACKGROUND OF THE INVENTION

This invention relates to an apparatus for controlling the dose ofirradiation designed for controlling the dose of electron rays to beirradiated to a synthetic resin product such as a bottle or a film orits preform in order to eliminate the monomers contained in it as wellas the dose of ultraviolet or infrared rays to be irradiated to such aproduct of surface treatment, material treatment or sterilization.

With an object of eliminating the monomers contained in synthetic resinproducts, their preforms are normally carried through an electron raysirradiation zone on a belt conveyer in a production line. A number ofconveyers arranged in parallel may be arranged to pass through such anelectron rays irradiation zone, each of the conveyers carrying productsof a type which is different from those of the other conveyers.

With such an arrangement, the amount of electron rays to be irradiatedto products should be differentiated depending on the thickness andshape of the products and other considerations. Such differentiation ofdose of electron rays is normally realized by moving the belt conveyersat different speeds to optimize the duration of exposure to eachproducts in the irradiation zone, the speed of each of the beltconveyers being appropriately selected to meet the required amount ofelectron rays for the preforms on it.

With a conventional apparatus for exposure of products to electron raysor other rays, the number of products that can be fed to a conveyer perunit time often differs from the number of products that can be treatedby electron rays per unit time. Thus, such discrepancy results incongestion of products on belt conveyers and accidental fall of some ofthem from the conveyers, arising in trouble such as a poor productivityof the production line.

In other words, if a plurality of conveyers are installed within aproduction line, the number of products fed to each of the conveyers isa function of their size and shape while the speed at which each of theconveyers is operated is a function of the dose required by the productsbeing carried on it and there are not any existing apparatuses thatsimultaneously satisfy these two functional requirements, entailing toopoorly fed conveyers that operate at a high speed and too heavily fedconveyers that operate at a low speed and accompanied by the problem ofcongestion and occasional accidents.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an apparatus forcontrolling the dose of irradiation that can accurately control the doseof electron rays, ultraviolet rays, infrared rays or other rays to meetthe exposure requirements of the products in a production line andtherefore eliminate the problem of congestion and occasional accidentsas described above.

According to the invention, the above object of the invention isachieved by providing an apparatus for controlling dose of irradiationcomprising a first barrier body arranged between a conveyer and anirradiation device located opposite to the conveyer, the first barrierbody being slidably movable along a running direction of the conveyer,and a second barrier body arranged in juxtaposition with the firstbarrier body and slidably movable along the running direction of theconveyer, a distance between the first barrier body and the secondbarrier body being so adjustable as to control the dose of irradiationto the product.

Alternatively, the first barrier body and the second barrier body havethe same configuration and are vertically juxtaposed, and each bodycomprises a plurality of oblique sections arranged oblique to therunning direction of the conveyer.

Still alternatively, the first and second barrier bodies may be formedin the form of flat plates which are horizontally juxtaposed along themoving direction of the conveyer.

Each of the first and second barrier bodies may alternatively be soconfigured that it comprises a conduit for cooling water to circulatethrough its entire internal area.

With an apparatus for controlling the dose of irradiation according tothe invention, where a product is exposed to electron rays irradiated bythe irradiation device as it moves on the conveyer, the product can beexposed to electron rays to a maximum extent by removing the first andsecond barrier bodies from the electron rays irradiation zone through asliding action.

When the dose of the product should be limited to a given extent, it canbe controlled by moving the first and second barrier bodies until thegap between the two barrier bodies meets the required dose so that theproduct is exposed only to those electron rays that come through thegap.

When, alternatively, the first and second barrier bodies are identicallyformed and vertically juxtaposed, each comprising a plurality of obliquesections, they may be placed in a completely overlapped position througha sliding action between the irradiation device and the conveyer tomaximize the gap through which electron rays can pass and therefore theexposure of the product to the rays (See FIGS. 2 and 4). For limitingthe dose of the product, the first and second barrier bodies are movedrelative to each other along the moving direction of the conveyerthrough a sliding action so that any two corresponding oblique sectionsof the barrier bodies that have been overlapped are now separated fromeach other to reduce the area of the gaps between any adjacent sectionsand hence to limit the exposure of the product to electron rays to adesired level.

When, still alternatively, the first and second barrier bodies areformed in the form of flat plates which are horizontally juxtaposedalong the moving direction of the conveyer, the gap between the twoplates can be increased by separating them away from each other toconsequently increase the dose of the product on the conveyer.Conversely, the dose can be reduced by bringing the two plates closer toeach other and reducing the gap between them.

When each of the first and second barrier bodies are provided with aconduit for cooling water to run through its entire internal area, theycan be effectively cooled even if they are excessively heated by theirradiated electron rays. Since the water is constantly circulatedthrough the conduit in each of the barrier bodies, any danger for thewater to emit heat due to the air bubbles formed in the water throughirradiation of electron rays is effectively eliminated.

Now the invention will be described in greater detail by referring tothe accompanying drawings that illustrate preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a first embodiment of theinvention.

FIG. 2 is a schematic perspective view of the first and second barrierbodies of the embodiment of FIG. 1, where the first and second barrierbodies are found in a completely overlapped position.

FIG. 3 is a perspective view similar to FIG. 2 but showing the first andsecond barrier bodies separated from each other.

FIG. 4 is a cross sectional view of part of the first and second barrierbodies under the condition of FIG. 2, where the two barrier bodies arecompletely overlapped.

FIG. 5 is a cross sectional similar to FIG. 4 but showing that the twobarrier bodies are separated from each other.

FIG. 6 is a schematic perspective view of a second embodiment of theinvention, showing that the first and second barrier bodies arecompletely overlapped.

FIG. 7 is a schematic perspective view similar to FIG. 6 but showingthat the first and second barrier bodies are slightly separated fromeach other.

FIG. 8 is a cross sectional view of part of the embodiment of FIG. 6under the condition where the two bodies are slightly separated fromeach other.

FIG. 9 is schematic perspective view of a third embodiment of theinvention.

FIG. 10 is a cross sectional view of part of the embodiment of FIG. 9.

FIG. 11 is a view illustrating the conduit provided in the barrierbodies according to the invention.

FIG. 11A is an enlarged partial view of the conduit shown in FIG. 11.

PREFERRED EMBODIMENT OF THE INVENTION

Referring to FIGS. 1 through 5 that illustrate a first preferredembodiment of the invention, the apparatus of the first embodiment isplaced immediately below an electron rays irradiation device 6 foreffectively removing monomers from a preform 4 of a synthetic resinproduct by means of electron rays irradiated from the irradiation device6. A first barrier body 1 and a second barrier body 2 have the sameconfiguration, each has a plurality of oblique sections 3 arrangedoblique to the moving direction of a conveyer 5. The first and secondbarrier bodies 1, 2 are vertically juxtaposed and each of them comprisesa serpentine stainless steel pipe which is folded for a number of timesto form a zigzag route. Cooling water passes through the pipe. Thestainless steel pipe is made of SUS304 of Japanese Industrial Standardswith an object of preventing rust formed on the surface thereof underthe influence of ozone to be generated by electron rays.

The angle of the oblique sections 3 relative to the moving direction ofthe conveyer 5 is preferable between 15° and 90°, but is not limitedthereto.

In this embodiment, the conveyer 5 includes a number of buckets forreceiving a preform 4 (not shown). Each bucket carries the preform 4therein while the preform 4 is constantly rotated so that it is evenlyexposed to electron rays in the bucket.

The present invention is not limited to the case in which preformscarried by the conveyer are rotated. The case in which the carriedpreform is not rotated is included in the present invention.

Now, a second preferred embodiment of the invention will be described byreferring to FIGS. 6 through 8.

Like the first embodiment, first and second barrier bodies 1 and 2 inthis second embodiment have the same configuration, and are verticallyjuxtaposed. Each barrier body comprises a rectangular shaped frame and aplurality of oblique sections 3 obliquely arranged relative to lateraland longitudinal members of the frame. The frame members and obliquesections 3 are hollow in cross section and communicate with one anotherto form a complete route for circulation of cooling water that runsthrough them from an end to the other end of the route.

FIGS. 9 through 11 shows a third embodiment of the invention. In thisembodiment, the first and second barrier bodies 1 and 2 are formed inthe form of flat plates and horizontally juxtaposed along the runningdirection of the conveyer 5. The dose of the irradiation of the electronrays to the product 4 can be increased by separating the body 1 and thebody 2 far apart from each other or reduced by bringing them close toeach other. Each of the barrier bodies 1 and 2 is formed with a conduit7 through which cooling water runs so that the barrier body may beeffectively cooled.

It may be needless to say that an apparatus for controlling the dose ofirradiation according to the invention is applicable not only to controlof the dose of electron rays of synthetic resin products but also tothat of ultraviolet or infrared rays to be used for surface treatment ormaterial treatment.

It may also be needless to say that the use of an apparatus forcontrolling the dose of irradiation according to the present inventionis not limited to preforms of synthetic resin bottles or films butapplicable to those of synthetic resin tubes and other forms as well asto metal products, paper products and so on.

As is apparent from the above description, since an apparatus forcontrolling the dose of irradiation according to the present inventioncan control the dose of electron rays, ultraviolet rays, infrared raysand the like for products by adjusting the gap between its first andsecond barrier bodies, the running speed of a conveyer carrying theproducts can be determined so as to match the rate of supply of productsmaking it unnecessary to reduce the speed of the conveyer to maximizethe dose for the products. Consequently, with an apparatus according tothe invention, the problem of congested production lines and reducedline productivity is completely eliminated.

Moreover, since each of the first and second barrier bodies is providedwith a conduit for circulation of cooling water, they can be effectivelycooled even if they are undesirably heated by electron rays and anybubbles of water that can be formed in the water and store heat can beeffectively moved away to eliminate any danger of storage of excessiveheat within the barrier bodies. Therefore, an apparatus for controllingthe dose of irradiation according to the present invention is highlydurable and hence remarkably cost effective.

What is claimed is:
 1. An apparatus for controlling a dose ofirradiation to a product comprising a first barrier body arrangedbetween a conveyer and an irradiation device located opposite to saidconveyer, said first barrier body being slidably movable along a runningdirection of said conveyer, and a second barrier body arranged injuxtaposition with said first barrier body and slidably movable alongthe running direction of said conveyer, a distance between said firstbarrier body and said second barrier body being adjustable forcontrolling the dose of irradiation to the product, wherein at least oneof said first and second barrier bodies has a conduit integrally formedtherein for circulation of cooling fluid within said body and said firstbarrier body and second barrier body have a same configuration and eachof said first barrier body and said second barrier body comprises aplurality of oblique sections arranged obliquely to the runningdirection of said conveyer.
 2. The apparatus for a dose of irradiationaccording to claim 1, wherein said first barrier body and said secondbarrier body are vertically juxtaposed.
 3. The apparatus for controllinga dose of irradiation according to claim 1, wherein said first andsecond barrier bodies are serpentine conduits.
 4. The apparatus forcontrolling a dose of irradiation according to claim 1, wherein saidfirst and second barrier bodies comprise a frame with oblique sectionsarranged between opposed sides of said frame in a spaced generallyparallel relationship.
 5. The apparatus for controlling a dose ofirradiation according to claim 1, wherein said first and second barrierbodies are plates and said conduits are serpentine passages extendingacross the length and width of said plates.
 6. The apparatus forcontrolling a dose of irradiation according to claim 1, wherein saidfirst and second bodies are obliquely arranged at an angle of betweenabout 15° and 90° to the running direction of the conveyer.
 7. Anapparatus for controlling a dose of irradiation comprising:anirradiation device; a conveyer extending under said irradiation device,said conveyer being fed objects at a predetermined feed rate and saidconveyer transporting said objects in a running direction a conveyerextending under said irradiation device, said conveyer being fed objectsat a predetermined feed rate and said conveyer transporting said objectsin a running direction at a conveyer speed determined by said feed rateunder said irradiation device; a first barrier body arranged betweensaid conveyer and said irradiation device, said first barrier body beingslidably movable along the running direction of said conveyer; a secondbarrier body slidably movable along the running direction of saidconveyer and arranged in juxtaposition with said first barrier body,wherein relative movement between said first barrier body and saidsecond barrier body is used to control irradiation to each of theobjects travelling in the running direction at said conveyer speed suchthat each of said objects receives a required dose of irradiation, saidfirst barrier body and said second barrier body having a sameconfiguration and each of said first barrier body and said secondbarrier body comprising a plurality of oblique sections which arearranged obliquely to the running direction of said conveyer.
 8. Theapparatus for controlling a dose of irradiation according to claim 7,wherein said oblique sections have an angle oblique to the runningdirection of said conveyer of between about 15° and 90°.
 9. Theapparatus for controlling a dose of irradiation according to claim 7,wherein said first and second barrier bodies are formed with integralconduits therein for circulation of cooling fluid within said bodies.10. The apparatus for controlling a dose of irradiation according toclaim 7, wherein said first and second barrier bodies are serpentineconduits.
 11. The apparatus for controlling a dose of irradiationaccording to claim 7, wherein said first and second barrier bodies eachcomprise a frame with oblique sections arranged between opposed sides ofsaid frame in a spaced generally parallel relationship, said frame andsaid oblique sections being hollow and in communication with each otherfor circulation of a cooling fluid.
 12. The apparatus for controlling adose of irradiation according to claim 7, wherein said first and secondbarrier bodies are plates each having a serpentine conduit integrallyformed therein for circulation of a cooling fluid.
 13. The apparatus forcontrolling a dose of irradiation according to claim 7, wherein saidfirst and second bodies are horizontally juxtaposed along the runningdirection of said conveyer.
 14. The apparatus for controlling a dose ofirradiation according to claim 7, wherein said predetermined feed rateis set at a maximum and said conveyer speed is set to correspond to saidmaximum feed rate.